Leaks in conduits carrying fluid in a distribution network, including for example water, oil, or chemicals, can result in significant lost revenues and increased cost for the operator of the network, such as a water utility. Without a systematic method for detection and repair, leaks may go undetected for a prolonged period time and become worse, thereby exacerbating the loss of revenue and cost of repair.
To detect leaks, detection units and systems have been used that are temporarily clamped onto the pipe. However, such systems detect leaks only in the proximate location where they are clamped on and only for the period of time they are in use on the pipe. What is needed is a long-term leak detection method that does not require the use of temporary leak detection units as a first line of detection. Moreover, in order to implement the detection method in a cost-effective manner, it is preferable that the method make use of existing technology or infrastructure to avoid having to retrofit every conduit in a utility system with a new piece of leak detection equipment.
Flow meters are typically found in any fluid distribution network carrying any valuable commodity, such as water, gas, steam, oil, or other chemicals. Under typical use, a flow meter measures the fluid flowing past a certain point in the conduit, such as at a branch in the network, an entry or exit to a distinct section of a network, and at a point of consumption in the network such as the premises of a residential, business, or industrial consumer. In a water distribution network operated by a utility, a flow meter allows the utility to charge the customer for the water consumed. In the petrochemical context, a flow meter may allow an operator to meter production of oil pumped from an oil well. Flow meters present in the other locations of a distribution network monitor and meter fluid flow and usage across the network.
One type of flow meter used in fluid distribution networks is an ultrasonic flow meter. A typical ultrasonic flow meter has at least one pair of ultrasonic transducers on a segment of pipe or conduit, with one transducer located upstream and the other downstream with respect to the direction of fluid flow in the pipe. Each of the pair of ultrasonic transducers typically sends and receives an ultrasonic pulse, or series of ultrasonic pulses, back and forth. That is, the first transducer in the pair generates a pulse, or series of pulses, which is received by the other transducer. The time of flight of each pulse, or the average time of flight of the pulses in the series of pulses, is measured. The second ultrasonic transducer then sends a pulse, or series of pulses, to the first transducer. Again, the time of flight is measured. In operation, a typical flow meter sends these pulses in each direction at least two to four times per second, every second, which provides repetitive and regular readings of the flow rate. The fluid flow causes the pulses traveling downstream (i.e., with the fluid flow) to move faster, and those traveling upstream (i.e., against the fluid flow), to move slower, than the speed of sound in the static fluid. Thus, the rate of flow can be determined based upon the difference in flight time between the pulses moving downstream and those moving upstream. Because the speed of sound in a fluid is dependent on the temperature of the fluid, accuracy of the meter can vary with temperature if the meter is not calibrated to temperature. However, if properly calibrated, the flow meter accurately and non-invasively determines the flow rate at any given time, thereby allowing calculation of the water consumption during a chosen period of time.
Flow meters often include a meter interface unit (MIU) capable of receiving and storing flow information and other data from the meter register itself and communicating this information externally. The MIU may be integrated with the meter register or provided as a separate unit that interfaces with the meter register. A typical MIU includes a processor for carrying out prescribed measurement and housekeeping routines and for performing the actions instructed from external devices, and a memory or other data storage for storing consumption and other information related to such instructions. In many cases, an MIU includes a transceiver for sending and receiving communications to and from external devices over a communications network 100, which may be wired or wireless. Such external devices may include a handheld or mobile reader, a fixed collector or repeater installed in the network, MIUs of other meters, a host system, or any combination of these devices. Communications between or among devices may be direct or indirect according to various protocols that have been developed. A host system may receive flow information from a large network of flow meters across the distribution network. In a typical system, the host receives packets of information from flow meters and can cause instructions to be sent directly or indirectly to a particular meter or set of meters. Similarly, a mobile or handheld reader may be used by a technician to send instructions to or obtain information from one or more meters. A fixed network system using MIUs, collectors, and a host system is described in co-owned U.S. Pat. No. 8,350,717. It should be understood, however, that the teachings of this disclosure, and embodiments of the invention described herein are not limited to a system as described in the referenced patent and may be used with any other meter communications architecture and protocols, including for example mesh networks.